A mass spectrometry (MS) system in general includes an ion source for ionizing molecules of a sample of interest, followed by one or more ion processing devices providing various functions, followed by a mass analyzer for separating ions based on their differing mass-to-charge ratios (or m/z ratios, or more simply “masses”), followed by an ion detector at which the mass-sorted ions arrive. An MS analysis produces a mass spectrum, which is a series of peaks indicative of the relative abundances of detected ions as a function of their m/z ratios.
In the serial process flow through the internal chambers of these devices, ions and gas molecules encounter various internal surfaces and pass through various ion optics components. Over time as the surfaces continue to be exposed to the flow of the ions and gas molecules, including surfaces of the ion optics components, layers of residual material may be deposited on these surfaces. Such layers can be electrically insulating, and may further be dielectric. Consequently, the outermost surface of the deposited layers can build up electrical charge from the charge of the ions deposited on its surface. As this electrical charge increases so does the potential (voltage) to the point that it can disrupt the nominal electric field of the affected component and cause a reduction in the transmission of the ions through the component. The contamination can lead to a degradation in the ion signal utilized to produce mass spectra, such as a decrease in signal intensity and resolution. The reduction in the signal is time dependent and can progress to the point that the entire signal is blocked. In some cases, the contamination problem has been observed to result from ionizing organic molecules such as certain types of analytes (e.g., proteins), background matrix materials such as solvents, and oil molecules from the vacuum pumps. The accumulation of such contaminants on surface is thus highly undesirable.
The conventional approach to cleaning a contaminated surface requires that the contaminated surface be removed from the MS system and cleaned externally. This requires shutting down operation of the system and venting the system to break vacuum, then opening or disassembling some part of the system to access the component containing the contaminated surface, and removing the component from the system. Removal of the component often requires disassembly of features utilized for mounting and setting the optical alignment of the component. Once removed, the contaminated surface is cleaned using an abrasive or solvent as needed, and then re-installed in the system with proper mounting and alignment. Then the system must be pumped back down to the vacuum levels required for operation, and re-tuned as needed to accommodate the newly cleaned surface. Thereafter, the system must be re-tuned as necessary for accommodating a new building up of contaminants on the surface, until such time as it is necessary to shut down the system again and repeat the cleaning procedure. The conventional cleaning approach thus results in significant loss of operating time, mechanical wear and fatigue on components, the use of hazardous compounds such as cleaning solvents, and the potential for exposing users to hazardous compounds.
Therefore, there is a need for MS systems and methods capable of cleaning internal surfaces. In particular, there is a need for MS systems and methods capable of cleaning internal surfaces in situ.